This invention relates to the adjustment of optical elements in a multi-axis imaging system, particularly the optical elements of an array microscope.
In a multi-axis imaging system, as that term is used herein, a plurality of optical elements are arranged in an array so as to image respective portions of a common object. One advantage of such a system is that all of the elements of the array can have a fixed relationship to one another and may be moved in unison to scan an object and bring its image into focus at a desired image plane. In particular, in an array microscope an array of miniature microscope objectives is employed instead of a single objective to achieve high resolution, without the mechanical drawbacks of a single, equivalent objective, and to scan a large field of the object more rapidly than can be achieved with a single objective. Such an array microscope is disclosed in PCT Patent Publication No. WO 02/075370, published Sep. 26, 2002.
The performance of an optical system is dependent on how well the lenses are aligned, both laterally and axially. The performance is also dependent on the symmetry of lenses. In the case of a single-axis optical system, axial and lateral alignment of the lenses is straightforward. However, in a multi-axis imaging system, separate alignment of individual optical elements, and lenses within an optical element, is inherently counter to the concept of disposing the optical elements of an array in a fixed relationship so that that they can be moved in unison and, thence, presents a difficult challenge.
Yet, individual alignment of the elements of a multi-axis imaging system would be desirable to overcome a number of performance problems. One such problem is that it is difficult to construct an array of lenses wherein all of the lenses are laterally spaced within an acceptable tolerance. Consequently, random displacement of the images of respective elements may degrade system performance. Another problem is that it is difficult to construct an array of lenses all of which are the same shape within an acceptable tolerance. Again, random variation in lens shapes may degrade system performance.
A problem of particular importance in microscopes is that either the thickness of the glass slide on which a specimen is mounted, or the surface of the specimen itself, may be sufficiently non-uniform that the portion of interest of one portion of an object may lie outside the depth of field of the microscope when focused on another portion of the object. It is straightforward to compensate for this non-uniformity with a single-axis optical system by simply refocusing the system when the object, or the system, is moved laterally. However, in an array microscope the overall field of view may be such that, because of slide or object non-uniformities, portions of an object imaged by one set of optical elements may be in focus, while other portions of the object imaged by another set of optical elements are out of focus, thereby degrading the overall image of the object.
Accordingly, there is a need for a multi-axis imaging system that provides the advantages of both moving the elements of the array in unison, and adjusting the adjusting the array elements individually.